[Automatic contrast limiting circuit and method thereof with spatial domain infinite impulse response filter]

Abstract

An automatic contrast limiting circuit and method thereof with spatial domain infinite impulse response filter are disclosed. A spatial domain infinite impulse response filter is adapted to generate an output value of the spatial domain infinite impulse response filter related to an input signal. A peak value detector is adapted to detect the peak output value of the spatial domain infinite impulse response filter during a predetermined recording interval. A contrast evaluator is used to evaluate the required contrast value referring to a predetermined threshold value and the output value of the spatial domain infinite impulse response filter.

1. An automatic contrast limiting circuit with a spatial domain infinite impulse response filter, for evaluating a contrast value, comprising:
 a spatial domain infinite impulse response filter, for receiving an input signal for generating a spatial domain infinite impulse response filtering value; 
 a peak value detector, coupled to the spatial domain infinite impulse response filter, for generating a peak value during a predetermined recording interval corresponding to the spatial domain infinite impulse response filtering value; and 
 a contrast evaluator, coupled to the peak value detector, for evaluating the contrast value according to the peak value and a predetermined threshold, 
 wherein when the contrast evaluator determines the peak value higher than the predetermined threshold, the contrast value is 1; otherwise, the contrast value is a value of the predetermined threshold divided by the peak value. 
 
   
   
     2. An automatic contrast limiting circuit with a spatial domain infinite impulse response filter, for evaluating a contrast value, comprising:
 a spatial domain infinite impulse response filter, for receiving an input signal for generating a spatial domain infinite impulse response filtering value; 
 a peak value detector, coupled to the spatial domain infinite impulse response fitter, for generating a peak value during a predetermined recording interval corresponding to the spatial domain infinite impulse response filtering value; 
 a contrast evaluator, coupled to the peak value detector, for evaluating the contrast value according to the peak value and a predetermined threshold, 
 a front-end spatial domain infinite impulse response filter, for receiving a front-end input signal for generating a front-end spatial domain infinite impulse response filtering value; and 
 a front-end peak value detector, coupled to the front-end spatial domain infinite impulse response filter for generating a front-end peak value during a front-end predetermined recording interval to be the input signal of the spatial domain infinite impulse response filter according to the spatial domain infinite impulse response filtering value. 
 
   
   
     3. An automatic contrast limiting circuit with a spatial domain infinite impulse response filter, for evaluating a contrast value, comprising:
 a spatial domain infinite impulse response filter, for receiving an input signal for generating a spatial domain infinite impulse response filtering value; 
 a peak value detector, coupled to the spatial domain infinite impulse response filter, for generating a peak value during a predetermined recording interval corresponding to the spatial domain infinite impulse response filtering value; 
 a contrast evaluator, coupled to the peak value detector, for evaluating the contrast value according to the peak value and a predetermined threshold, 
 a front-end spatial domain infinite impulse response filter, for receiving a front-end input signal for generating a front-end spatial domain infinite impulse response filtering value; and 
 a front-end peak value detector, coupled to the front-end spatial domain infinite impulse response filter for generating a front-end peak value during a front-end predetermined recording interval to be the input signal of the spatial domain infinite impulse response filter according to the spatial domain infinite impulse response filtering value, 
 wherein the front-end spatial domain infinite impulse response filter comprises:
 a first multiplier, for multiplying the front-end input signal with a first factor value for generating a first output value; 
 an adder, coupled to the first multiplier for generating a sum of the first output value and a second output value to be the front-end spatial domain infinite impulse response filtering value; and 
 a second multiplier, for multiplying the front-end spatial domain infinite impulse response filtering value with a second factor value for generating the second output value, wherein a sum of the first factor value and the second factor value is 1. 
 
 
   
   
     4. An automatic contrast controlling method of a spatial domain infinite impulse response filter, adapted to evaluate a contrast value, comprising:
 receiving an input signal for generating a spatial domain infinite impulse response filtering value; 
 generating a peak value during a recoding interval according to the spatial domain infinite impulse response filtering value; and 
 
     evaluating the contrast value according to the peak value and a predetermined threshold, 
     wherein when the peak value is higher than the predetermined threshold, the contrast value is 1; otherwise, the contrast value is a value of the predetermined threshold divided by the peak value.